I think it could totally be doable to twin-charge an m42. They already make a supercharger kit for the m42, and turbos are pretty simple and I bet there is a kit out there as well. The supercharger would be on the intake side of the engine and the turbo would be on the exhaust side and I don't see plumbing being that hard, and I have seen v12's stuffed in an e30 so I know it will fit one way or another.....but then, that is a stupid amount of money to throw at an m42 vs swapping in an s52 or ls1 IMO.